This bit of good news, at least, appears to be true: Although the Sapir Organization has not officially announced the deal, school officials said on Feb. 27 that papers had been signed and its inaugural class would start in the fall. The landlord also announced another recent deal, signed in December, a 65,000-square-foot lease with Interactive Data Corporation.

It’s been a long haul for 100 Church to this spate of positivity. Bought by real estate magnate (and former taxi driver) Tamir Sapir for $65 million in 1997, 100 Church has gone through more crises and reinventions than Oprah: Only two major tenants returned after the building was devastated in the attacks on the nearby World Trade Center, and leasing has since been glacial, leaving the building over 50 percent vacant and the emptiest in downtown.

The Sapirs briefly considered taking the building residential, and decided again on commercial when the office market ticked up in 2006. Cushman & Wakefield was retained to remarket the building in 2006, and was dropped for CB Richard Ellis in 2007. Along the way, several high-profile leases disintegrated: a group of toy industry firms in 2005, the Omnicom Group in 2007, and Newsweek in 2008 all fell through.

Claremont Prep, it would seem, is a heavenly match—and also a concession to the commercial reality, which has midtown office rents at historic lows and downtown becoming increasingly popular for families, as a recent Times article pointed out. Owner MetSchools Inc. wanted something within walking distance of its primary and middle school at 41 Broad Street. School officials expect to slowly fill 100 Church’s ninth and 10th floors with about 480 students while they build an underground aquatics facility, rooftop basketball courts, a black box theater, and another whole floor on the top of the building.

“I think the good news for us is that they’ve got a separate entrance,” said Mark Hepsworth, president of institutional business for Interactive Data, which signed not long before.

INLAID IN THE FLOOR OF 100 Church’s multimillion dollar new lobby is a gigantic globe of multicolored stone, inscribed in what looks like bronze with the words, “THE SAPIR ORGANIZATION.” The landlord’s mark is evident elsewhere: a large circular plaque on an outside column, custom floor mats with the emblem of a big cat; the lobby itself is almost tsarist in its luxury, with Swarovski crystal starbursts and a sweeping stone fountain.

The drab 1950s exterior has yet to quite catch up, but it’s trying. Windows are being replaced floor by floor, and an Italian company is hand-painting each of the flat blue panels to look like marble. It’s all part of an aggressive campaign to position the building, still the emptiest of Sapir’s nine Manhattan holdings.

But the journey has been at times bumpy and publicly so. Sapir has been sued by Newmark Knight Frank and CBRE over unpaid commissions, and that kind of reputation—coupled with being relatively new to the game—dies hard. “They’re a tough landlord,” said one tenant-side broker who asked to remain anonymous. “In this market, I’ve got options. And I’m going to drive them towards landlords who have been really solid members of the community for a long time. … People who don’t play fair, who don’t pay their commissions on time, people remember that.”

Not so, says Sapir managing director Mark Kozhin. “The current management is completely different from prior management,” he wrote in an email. “What happened in the past is no longer relevant.” (Alex Sapir could not be reached for comment.)

The building’s current leasing agent, Brad Gerla of CBRE, has explanations for all of the previous deals gone sour. The toy industry “couldn’t get their act together,” he said. “That deal was not a lost deal, that was a deal they never did.” And though Newsweek had signed, they backed out when a space on Hudson Street proved too attractive to resist. “It was never a deal that we lost for any reason other than the market had softened, and other spaces became available,” Mr. Gerla added.

By Mr. Gerla’s count, the building still has 300,000 square feet of available space. It’s leasing for $36 a square foot, according to CoStar.

With the added peculiarity of a school, 100 Church already has an odd tenant mix. Luxury magazine publisher Niche Media takes up the seventh floor, a well-lit and fashionably redone space with a legion of well-dressed, predominantly female 20-something employees. Below them are the 650-odd lawyers of the New York City Law Department, with offices that one employee described as “like an ordinary building, nothing fancy, nothing different.”

Most of the remaining small tenants work up on the 16th floor, including the Council of Jewish Émigré Community Organizations, which, according to one worker, occupies the space by the grace of Tamir Sapir, a Russian emigrant himself.